This invention relates to a digital radio receiver for receiving an electric wave from an artificial satellite (which may be called a xe2x80x9csatellite wavexe2x80x9d) or an electric wave on the ground (which may be called a xe2x80x9cground wavexe2x80x9d) to listen in a digital radio broadcasting and, in particular, to an antenna for use in the digital radio receiver.
In recent years, a digital radio receiver, which receives the satellite wave or the ground wave to listen in the digital radio broadcasting, has been developed and is put to practical use in the United States of America. The digital radio receiver is mounted on a mobile station such as an automobile and can receive an electric wave having a frequency of about 2.3 gigahelts (GHz) to listen in a radio broadcasting. That is, the digital radio receiver is a radio receiver which can listen in a mobile broadcasting. In addition, the ground wave is an electric wave in which a signal where the satellite wave is received in an earth station is frequently shifted a little.
In order to receive such an electric wave having the frequency of about 2.3 GHz, it is necessary to set up an antenna outside the automobile. Although such antennas have been proposed those having various structures, the antennas of stick-type are generally used rather than those of planer-type (plane-type). In addition, in the manner which is well known in the art, an electromagnetic wave radiated in a free space is a transverse wave having electric and magnetic fields which vibrate at right angles to each other in a plane perpendicular to the direction of motion and the electric field and the magnetic field have variable strength in the plane. A polarized wave is an electromagnetic radiation in which the direction of the electric field vector is not random. The satellite wave is a circular polarization while the ground wave is a linear polarization. Accordingly, exclusive antennas are required to receive both of the satellite wave and the ground wave.
Now, the description will be mainly made as regards the antennas for receiving the satellite wave. A helical or helix antenna is known in the art as one of the antennas of the stick-type. The helical antenna has structure where at least one antenna lead member is wound around an outer peripheral surface of a hollow or solid cylindrical (which is collectively called xe2x80x9ccylindricalxe2x80x9d) member in a helix fashion (spiral fashion), namely, is an antenna having the form of a helix. The cylindrical member may be merely called a xe2x80x9cbobbinxe2x80x9d or a xe2x80x9cdielectric corexe2x80x9d in the art. In addition, the antenna lead member may be merely called a xe2x80x9clead.xe2x80x9d The helical antenna can effectively receive the above-mentioned circular polarization. The cylindrical member or the bobbin is made of an insulation material such as plastics. In addition, the antenna lead members are equal, for example, in number to four. On the other hand, it is remarkably difficult to really wind the plurality of antenna lead members around the outer peripheral surface of the cylindrical member or the bobbin in the helix fashion. Accordingly, alternatively, another helical antenna is proposed in which an antenna pattern film where a plurality of conductive patterns are printed or formed on an insulation sheet or a flexible film is wound around the outer peripheral surface of the cylindrical member or the bobbin.
In general, the hollow cylindrical member is used rather than the solid cylindrical member. This is because the solid cylindrical member has a heavy weight and requires a large amount of material on manufacturing. However, a conventional helical antenna comprising the hollow cylindrical member is advantageous in that it has a weak structure in strength.
In addition, such as a helical antenna has a resonance frequency which is determined due to a height (length), a diameter, a relative dielectric constant (relative permittivity), and so on of the cylindrical member. Accordingly, in order to receive the satellite wave (circular polarization) having the frequency of about 2.3 GHz using the helical antenna, it is necessary to make a resonance point (or the resonance frequency of the helical antenna) equal to a desired resonance frequency of 2.3 GHz. However, inasmuch as variations in size are not avoided on a process of manufacturing the helical antenna, it is necessary to adjust the resonance frequency of the helical antenna to match the desired resonance frequency.
In prior art, a conventional adjustment method is a cutting method comprising the step of cutting a tip portion of the helical antenna to adjust the length of the helical antenna. However, the cutting method is disadvantageous in that it takes a lot of time in the manner which will later be described in detail.
In addition, a conventional helical antenna is manufactured by winding the antenna film pattern around the outer peripheral surface of the bobbin and by fixing the antenna film pattern on the bobbin by means of an adhesive tape, an adhesive agent, or the like. With this structure, the conventional helical antenna is advantageous in that the antenna film pattern may be peeled off the bobbin due to a long service and it is difficult to stably fix the antenna film pattern on the outer peripheral surface of the bobbin. In addition, when the helical antenna is mounted on the automobile, vibrations and shocks are given to the helical antenna. Under the circumstances, sufficient antivibration and anti-shockness are not obtained in the above-mentioned conventional helical antenna in which the antenna pattern film is fixed on the outer peripheral surface of the bobbin by means of the adhesive tape, the adhesive agent, or the like.
Attention will be directed to a four-phase feel helical antenna which has four antenna lead members wound around the outer peripheral surface of the bobbin. After the satellite wave is received by the four antenna lead members as four received waves, the four received waves are phase shifted and combined by a phase shifter so as to match phases of the four received waves to obtain a combined wave, and then the combined wave is amplified by a low-noise amplifier to obtain an amplified wave which is delivered to a receiver body. A combination of the four-phase feed helical antenna, the phase shifter, and the low-noise amplifier is called an antenna unit.
In addition, the helical antenna may have only one antenna lead member. In this event, the phase shifter is removed from the antenna unit. In other words, the antenna unit consists of the helical antenna and the low-noise amplifier.
A conventional antenna unit is provided with a bottom case which is Adisposed at a lower end of the helical antenna and in which the low-noise amplifier is received. Inasmuch as the bottom case is required in the conventional antenna unit, the bottom case hinders miniaturization of the antenna unit and restricts design of the antenna unit. In the conventional antenna unit, the phase shifter and the low-noise amplifier are constructed as separated parts and provided with connectors for connecting therebetween.
With this structure, assembling of the antenna unit is complicated and it is difficult to precisely evaluate performances at an output of the phase shifter and an input of the low-noise amplifier after assembling of the antenna unit.
In addition, a conventional antenna unit is provided with a ground plate having a plane shape on which the helical antenna is perpendicularly set up in the manner which will later be described in conjunction with FIGS. 39 and 40. Inasmuch as the ground plate has the plane shape, the conventional antenna unit is disadvantageous in that it is difficult to decrease ground noises and to improve an antenna sensitivity.
In order to receive both of the satellite wave and the ground wave, a special antenna unit comprising a helical antenna and a rod antenna is known in the art in the manner which will later be described in conjunction with FIG. 44. Such a special antenna unit is called a composite antenna unit. In the composite antenna unit, the helical antenna is for receiving the satellite wave or the circular polarization while the rod antenna is for receiving the ground wave or the linear polarization. Accordingly, the helical antenna may be called a circular polarization receiving antenna while the rod antenna may be called a linear polarization receiving antenna. In a conventional composite antenna, the circular polarization receiving antenna and the linear polarization receiving antenna are independently manufactured as independent parts. As a result, the conventional composite antenna is disadvantageous in that a lot of parts are required and a manufacturing cost is expensive.
It is therefore an object of the present invention to provide a helical antenna which is capable of strengthening in structure without weighting.
It is another object of the present invention to provide a helical antenna which is capable of easily adjusting a resonance frequency of the helical antenna.
It is still another of the present invention to provide a helical antenna which is capable of stably fixing an antenna pattern film on an outer peripheral surface of a bobbin.
It is yet another of the present invention to provide a helical antenna which is capable of accurately positioning an antenna pattern film on an outer peripheral surface of a bobbin.
It is a further object of the present invention to provide an antenna unit which is capable of easily miniaturizing the antenna unit.
It is a still further object of the present invention to provide an antenna unit which is capable of easily assembling the antenna unit.
It is a yet further object of the present invention to provide an antenna unit which is capable of precisely evaluating performances of the antenna unit.
It is an object of the present invention to provide an antenna unit which is capable of decreasing ground noises.
It is another object of the present invention to provide an antenna unit which is capable of improving an antenna sensitivity of the antenna unit.
It is still another object of the present invention to provide a composite antenna which is capable of reducing the number of parts.
It is yet another object of the present invention to provide a composite antenna which is capable of decreasing a manufacturing cost.
It is a further object of the present invention to provide a composite antenna which is capable of miniaturizing the composite antenna.
Other objects of this invention will become clear as the description proceeds.
According to a first aspect of this invention, a helical antenna comprises a hollow cylindrical member made of insulator. The hollow cylindrical member has a center axis extending in a longitudinal direction, an inner peripheral surface, and an outer peripheral surface. An antenna pattern film is wound around the outer peripheral surface of the cylindrical member. A center rod is coaxial with the center axis. Disposed between the center rod and the inner peripheral surface of the hollow cylindrical member, at least three ribs symmetrically extend in a radial manner at equal angular intervals. Instead of the antenna pattern film, at least one antenna lead member may be wound around the outer peripheral surface of the cylindrical member in a helix fashion.
According to a second aspect of this invention, a helical antenna comprises a hollow cylindrical member made of insulator. The hollow cylindrical member has a center axis extending in a longitudinal direction, an inner peripheral wall, and an outer peripheral wall. The hollow cylindrical member has an upper end portion. The hollow cylindrical member has a female threaded screw hole where the upper end portion of the cylindrical member is threaded in the inner peripheral wall of the hollow cylindrical member. At least one antenna lead member is wound around the outer peripheral wall of the hollow cylindrical member in a helix fashion. A male screw member is threaded in the female threaded screw hole. The male screw member has a relative permittivity which is not less than that of the hollow cylindrical member.
According to a third aspect of this invention, a method is of adjusting a resonance frequency of the helical antenna according to the second aspect of this invention into a desired resonance frequency. The method comprises the steps of preparing the hollow cylindrical member having a length in which the helical antenna enables to receive a frequency lower than the desired resonance frequency, and of threading the male screw member in the female threaded screw hole so as to adjust the resonance frequency of the helical antenna into the desired resonance frequency.
According to a fourth aspect of this invention, a helical antenna comprises a cylindrical dielectric core made of insulator. The cylindrical dielectric core has a center axis extending a longitudinal direction and an outer peripheral surface. An antenna lead member made of conductor is wound around the outer peripheral surface of the cylindrical dielectric core in a helix fashion except for a tip portion of the cylindrical dielectric core. A resonance frequency adjustment portion made of additional conductor is formed on the outer peripheral surface of the cylindrical dielectric core at the tip portion of the cylindrical dielectric core adjacent to the antenna lead member.
According to a fifth aspect of this invention, a helical antenna comprises a cylindrical dielectric core made of insulator. The cylindrical dielectric core has a center axis extending a longitudinal direction and an outer peripheral surface. The helical antenna further comprises first through N-th antenna lead members each made of conductor where N represents a predetermined positive integer which is not less than two. Each of the first through the N-th antenna lead members is wound around the outer peripheral surface of the cylindrical dielectric core in a helix fashion except for a tip portion of the cylindrical dielectric core. First through N-th resonance frequency adjustment portions, each of which is made of additional conductor, are formed on the outer peripheral surface of the cylindrical dielectric core at the tip portion of the cylindrical dielectric core adjacent to the first through said N-th antenna lead members, respectively.
According to a sixth aspect of this invention, a method is of adjusting a resonance frequency of a helical antenna comprising a cylindrical dielectric core made of insulator, an antenna lead member made of conductor, and a resonance frequency adjustment portion made of additional conductor. The cylindrical dielectric core has a center axis extending a longitudinal direction and an outer peripheral surface. The antenna lead member is wound around the outer peripheral surface of the cylindrical dielectric core in a helix fashion except for a tip portion of the dielectric core. The resonance frequency adjustment portion is formed on the outer peripheral surface of the cylindrical dielectric core at the tip portion of the cylindrical dielectric core adjacent to the antenna lead member. The resonance frequency adjustment portion comprises the additional conductor which is apart from a tip of the antenna lead member with a primary gap and which consists of a train of conductor segments with subsidiary gaps between adjacent conductor segments. The method comprises the step of electrically connecting the antenna lead member with the additional conductor at the primary gap and of electrically connecting between the adjacent conductor segments at the subsidiary gaps in the order of being apart from the tip of the antenna lead member to vary a length of an antenna lead, thereby adjusting the resonance frequency of the helical antenna.
According to a seventh aspect of this invention, a helical antenna comprises a cylindrical dielectric core made of insulator. The cylindrical dielectric core has a center axis extending in a longitudinal direction and a core outer peripheral surface. At least one antenna lead member made of conductor is wound around the core outer peripheral surface of the cylindrical dielectric core in a helix fashion. A hollow dielectric member covers an tip end portion of the cylindrical dielectric core with the antenna lead member sandwiched between the hollow dielectric member and the cylindrical dielectric core. The hollow dielectric member is movable along the longitudinal direction.
According to an eighth aspect of this invention, a helical antenna comprises a cylindrical dielectric core made of insulator. The cylindrical dielectric core has a center axis extending in a longitudinal direction and a core outer peripheral surface. At least one antenna lead member made of conductor is wound around the core outer peripheral surface of the cylindrical dielectric core in a helix fashion. A hollow cylindrical outer cover covers an assembly of the cylindrical dielectric core and the at least one antenna lead member. The hollow cylindrical outer cover has a cover outer peripheral wall on which a cover male threaded portion is threaded at a tip end portion thereof. A hollow dielectric member has a member inner wall on which a member female threaded portion is threaded. The hollow dielectric member is threaded on the hollow cylindrical outer cover so as to engage the member female threaded portion with the cover male threaded portion.
According to a ninth aspect of this invention, a method is of adjusting a resonance frequency of a helical antenna comprising a cylindrical dielectric core made of insulator, at least one antenna lead member made of conductor, and a hollow dielectric member covering an tip end portion of the cylindrical dielectric core with the antenna lead member sandwiched between the hollow dielectric member and the cylindrical dielectric core. The cylindrical dielectric core has a center axis extending in a longitudinal direction and a core outer peripheral surface. The antenna lead member is wound around the core outer peripheral surface of the cylindrical dielectric core in a helix fashion. The hollow dielectric member is movable along the longitudinal direction. The method comprises the step of moving the hollow dielectric member along the longitudinal direction so as to change a range where the at least one antenna lead member is covered by the hollow dielectric member, thereby adjusting the resonance frequency of the helical antenna.
According to a tenth aspect of this invention, a helical antenna comprises a cylindrical dielectric core made of insulator. The cylindrical dielectric core has a center axis extending in a longitudinal direction and an outer peripheral surface. An antenna pattern film is wound around the outer peripheral surface of the cylindrical dielectric core. The antenna pattern film comprises a flexible insulator film and a conductive pattern printed on the flexible insulator film. The conductive pattern has at least one antenna lead member so as to wind the at least one antenna lead member on the outer peripheral surface of the cylindrical dielectric core in a helix fashion. The at least one antenna lead member is made of conductor. The flexible insulator film is detachably pasted on the outer peripheral surface of the cylindrical dielectric core. The flexible insulator film has a plurality of circumferential perforated circular lines extending along a circumferential direction at a tip portion of the cylindrical dielectric core except for the conductive pattern at equal intervals in the longitudinal direction so as to form belts between adjacent circumferential perforated circular lines.
According to an eleventh aspect of this invention, a method is of adjusting a resonance frequency of a helical antenna according to the tenth aspect of this invention so as to match a desired resonance frequency. The method comprises the steps of preparing the cylindrical dielectric core having a length so that the helical antenna enables to receive a frequency lower than the desired resonance frequency, and of stripping the belts of the flexible insulator film in the order of being apart from a tip end of the cylindrical dielectric core to decrease a length of the conductive pattern, thereby matching the resonance frequency of the helical antenna with the desired resonance frequency.
According to a twelfth aspect of this invention, a helical antenna comprises a solid cylindrical dielectric core made of insulator. The solid cylindrical dielectric core has a center axis extending in a longitudinal direction and an outer peripheral surface. The solid cylindrical dielectric core has a dielectric constant higher than that of air. The solid cylindrical dielectric core has a tip end which is exposed so as to enable to dig up the solid cylindrical dielectric core along the longitudinal direction. At least one antenna lead member is wound around the outer peripheral surface of the solid cylindrical dielectric core in a helix fashion.
According to a thirteenth aspect of this invention, a method is of adjusting a resonance frequency of a helical antenna according to the twelfth aspect of this invention so as to match a desired resonance frequency. The method comprises the steps of preparing the helical antenna having a resonance frequency which is lower than the desired resonance frequency, and of digging up a center portion of the solid cylindrical dielectric core at the tip end to decrease an effective length of the solid cylindrical dielectric core, thereby matching the resonance frequency of the helical antenna with said desired resonance frequency.
According to a fourteenth aspect of this invention, a helical antenna comprises a cylindrical dielectric core made of insulator. The cylindrical dielectric core has a center axis extending in a longitudinal direction and an outer peripheral surface. The solid cylindrical dielectric core has a plurality of through holes for penetrating the outer peripheral surface in a radial direction at predetermined spaces along the longitudinal direction. An antenna pattern film is wound around the outer peripheral surface of the cylindrical dielectric core. A plurality of plastic rivet pins pass through the respective though holes to fix the antenna pattern film on the outer peripheral surface of the cylindrical dielectric core.
According to a fifteenth aspect of this invention, a helical antenna comprises a hollow cylindrical dielectric core made of insulator. The hollow cylindrical dielectric core has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The hollow cylindrical dielectric core has a slit which communicates between the outer peripheral surface and the inner peripheral surface and which extending along the longitudinal direction. An antenna pattern film is wound around the outer peripheral surface of the cylindrical dielectric core. The antenna pattern film has one side edge which is inserted in the hollow cylindrical dielectric core through the slit, thereby hooking the antenna pattern film on the hollow cylindrical dielectric core at the one side edge thereof.
According to a sixteenth aspect of this invention, a method is of fixing an antenna pattern film on a hollow cylindrical dielectric core made of insulator. The hollow cylindrical dielectric core has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The method comprises the steps of forming a slit in said hollow cylindrical dielectric core so as to communicate between the outer peripheral surface and the inner peripheral surface and to extend along the longitudinal direction, of inserting one side edge of the antenna pattern film in the slit of the hollow cylindrical dielectric core to hook the antenna pattern film on the hollow cylindrical dielectric core at the one side edge thereof, of winding the antenna pattern film around the outer peripheral surface of the cylindrical dielectric core, and of adhering another side edge of the antenna pattern film to a surface of the antenna pattern film to fix the antenna pattern film on the outer peripheral surface of the hollow cylindrical dielectric core.
According to a seventeenth aspect of this invention, a helical antenna comprises a hollow cylindrical dielectric core made of insulator. The hollow cylindrical dielectric core has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The hollow cylindrical dielectric core has a slit which communicates between the outer peripheral surface and the inner peripheral surface and which extending along the longitudinal direction. The hollow cylindrical dielectric core has a plurality of hooks at the inner peripheral surface with equal intervals in the longitudinal direction near the slit. An antenna pattern film is wound around the outer peripheral surface of the hollow cylindrical dielectric core. The antenna pattern film having a plurality of eyes near one side edge thereof along the longitudinal direction with equal intervals, thereby said antenna pattern film is hooked on the hooks of the hollow cylindrical dielectric core at the one side edge thereof with the hooks engaged with the corresponding eyes.
According to an eighteenth aspect of this invention, a method is of fixing an antenna pattern film on a hollow cylindrical dielectric core made of insulator. The hollow cylindrical dielectric core has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The method comprises the steps of forming a slit in the hollow cylindrical dielectric core so as to communicate between the outer peripheral surface and the inner peripheral surface and to extend along the longitudinal direction, of fitting a plurality of hooks to the hollow cylindrical dielectric core at the inner peripheral surface with equal intervals in the longitudinal direction near the slit, of forming a plurality of eyes in the antenna pattern film near one side edge of the antenna pattern film along the longitudinal direction with equal intervals, of inserting the one side edge of the antenna pattern film in the slit of the hollow cylindrical dielectric core, of hooking the one side edge of the antenna pattern film on the hooks with the hooks engaged with the corresponding eyes, of winding the antenna pattern film around the outer peripheral surface of the hollow cylindrical dielectric core, and of adhering another side edge of the antenna pattern film to a surface of said antenna pattern film to fix the antenna pattern film on the outer peripheral surface of the hollow cylindrical dielectric core.
According to a nineteenth aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and an antenna lead member made of conductor. The hollow cylindrical member has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead member is wound around the outer peripheral surface of the hollow cylindrical member in a helix fashion. A main circuit board is mounted inside said hollow cylindrical member near one end of the hollow cylindrical member in the longitudinal direction. A low-noise amplifier is mounted on the main circuit board. The low-noise amplifier has an amplifier input terminal connected to an end of said antenna lead member.
According to a twentieth aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and an antenna lead member made of conductor. The hollow cylindrical member has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead member is wound around the outer peripheral surface of the hollow cylindrical member in a helix fashion. A main circuit board is mounted inside the hollow cylindrical member near one end of the hollow cylindrical member in the longitudinal direction. The main circuit board has a principal surface which extends in parallel with the longitudinal direction. A low-noise amplifier is mounted on the principal surface of the main circuit board. The low-noise amplifier has an amplifier input terminal connected to an end of the antenna lead member.
According to a twenty-first aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and a plurality of antenna lead members made of conductor. The hollow cylindrical member has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead members are wound around the outer peripheral surface of the hollow cylindrical member in a helix fashion. A main circuit board is mounted inside the hollow cylindrical member near one end of said hollow cylindrical member in the longitudinal direction. The main circuit board has a principal surface which extends in parallel with the longitudinal direction. A phase shifter is supported on the hollow cylindrical member. The phase shifter has a plurality of shifter input terminals connected to ends of the antenna lead members and a shifter output terminal. A low-noise amplifier is mounted on the principal surface of the main circuit board. The low-noise amplifier has an amplifier input terminal connected to the shifter output terminal.
According to a twenty-second aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and a plurality of antenna lead members made of conductor. The hollow cylindrical member has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead members are wound around the outer peripheral surface of the hollow cylindrical member in a helix fashion. A main circuit board is mounted inside the hollow cylindrical member near one end of the hollow cylindrical member in the longitudinal direction. The main circuit board has a principal surface which extends in parallel with the longitudinal direction. A phase shifter is mounted on the principal surface of the main circuit board. The phase shifter has a plurality of shifter input terminals connected to ends of the antenna lead members and a shifter output terminal. A low-noise amplifier is mounted on the principal surface of the main circuit board. The low-noise amplifier has an amplifier input terminal connected to the shifter output terminal.
According to a twenty-third aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and a plurality of antenna lead members made of conductor. The hollow cylindrical member having a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead members are wound around the outer peripheral surface of the hollow cylindrical member in a helix fashion. A main circuit board is mounted inside the hollow cylindrical member near one end of said hollow cylindrical member in the longitudinal direction. The main circuit board has a main principal surface which extends in parallel with the longitudinal direction. A subsidiary circuit board is mounted within said hollow cylindrical member. The subsidiary circuit board has a subsidiary principal surface which extends in parallel with of the main principal surface of the main circuit board. A phase shifter is mounted on the subsidiary principal surface of the subsidiary circuit board. The phase shifter has a plurality of shifter input terminals connected to ends of the antenna lead members and a shifter output terminal. A low-noise amplifier is mounted on the main principal surface of the main circuit board. The low-noise amplifier has an amplifier input terminal connected to the shifter output terminal via a connection pin.
According to a twenty-fourth aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and an antenna lead member made of conductor. The hollow cylindrical member has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead member are wound around the outer peripheral surface of the cylindrical member in a helix fashion. A main circuit board is mounted inside the hollow cylindrical member near one end of the hollow cylindrical member in the longitudinal direction. The main circuit board has a principal surface which extends so as to intersect the longitudinal direction. A low-noise amplifier is mounted on the principal surface of the main circuit board. The low-noise amplifier has an amplifier input terminal connected to an end of said antenna lead member.
According to a twenty-fifth aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and a plurality of antenna lead members made of conductor. The hollow cylindrical member has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead members are wound around the outer peripheral surface of the cylindrical member in a helix fashion. A main circuit board is mounted inside the hollow cylindrical member near one end of the hollow cylindrical member in the longitudinal direction. The main circuit board has a principal surface which extends so as to intersect the longitudinal direction. A phase shifter is supported on the hollow cylindrical member. The phase shifter comprises a plurality of shifter input terminals connected to ends of the antenna lead members and a shifter output terminal. A low-noise amplifier is mounted on the principal surface of the main circuit board. The low-noise amplifier has an amplifier input terminal connected to the shifter output terminal.
According to a twenty-sixth aspect of this invention, an antenna unit comprises a helical antenna comprising a hollow cylindrical member made of insulator and a plurality of antenna lead members made of conductor. The hollow cylindrical member has a center axis extending in a longitudinal direction, an outer peripheral surface, and an inner peripheral surface. The antenna lead members are wound around the outer peripheral surface of the cylindrical member in a helix fashion. A main circuit board is mounted inside the hollow cylindrical member near one end of the hollow cylindrical member in the longitudinal direction. The main circuit board has a main principal surface which extends so as to intersect the longitudinal direction. A subsidiary circuit board is mounted within the hollow cylindrical member. The subsidiary circuit board has a subsidiary principal surface which extends in parallel with the main principal surface of the main circuit board. A phase shifter is mounted on the subsidiary principal surface of the subsidiary circuit board. The phase shifter has a plurality of shifter input terminals connected to ends of the antenna lead members and a shifter output terminal. A low-noise amplifier is mounted on the main principal surface of the main circuit board. The low-noise amplifier has an amplifier input terminal connected to the shifter output terminal via a connection pin.
According to a twenty-seventh aspect of this invention, an antenna unit comprises a helical antenna including a plurality of antenna lead members, a phase shifter having a plurality of shifter input terminals connected to ends of the antenna lead members of the helical antenna and a shifter output terminal, and a low-noise amplifier having an amplifier input terminal connected to the shifter output terminal. The antenna unit comprises a circuit board having a principal surface on which the phase shifter and the low-noise amplifier are mounted. The circuit board includes first and second conductive connection strips formed on the principal surface. The first and the second conductive connection strips have one ends connected to the shifter output terminal and the amplifier input terminal, respectively. The first and the second conductive connection strips have other ends which are opposed to each other with a predetermined space. A conducting member electrically connects between the other ends of the first and the second conductive connection strips.
According to a twenty-eighth aspect of this invention, a method is of manufacturing an antenna unit comprising a helical antenna including a plurality of antenna lead members, a phase shifter having a plurality of shifter input terminals connected to ends of the antenna lead members of the helical antenna and a shifter output terminal, and a low-noise amplifier having an amplifier input terminal connected to the shifter output terminal. The method comprises the steps of preparing a circuit board having a principal surface for mounting the phase shifter and the low-noise amplifier, of forming, on the principal surface of the circuit board, the phase shifter with the shifter output terminal and the low-noise amplifier with the amplifier input terminal, of forming, on the principal surface of the circuit board, first and second conductive connection strips having one ends connected to the shifter output terminal and the amplifier input terminal, respectively, the first and the second conductive connection strips having other ends which are opposed to each other with a predetermined space, and of electrically connecting between the other ends of the first and the second conductive connection strips using a conducting member.
According to a twenty-ninth aspect of this invention, an antenna unit comprises a cylindrical antenna having a center axis extending in a longitudinal direction. The cylindrical antenna having a tip portion and a rear portion. A bottom case supports the cylindrical antenna so as to raise the cylindrical antenna with the rear portion of the cylindrical antenna inserted within the bottom case. A ground plate is mounted on a base of the bottom case so as to intersect the longitudinal direction. The ground plate comprises a main plate part having a main area wider than a cross section of the cylindrical antenna and a subsidiary plate part projecting toward the cylindrical antenna at a peripheral edge of the main plate part.
According to a thirtieth aspect of this invention, a composite antenna comprises a cylindrical member made of insulator. The cylindrical member has a center axis extending in a longitudinal direction and an outer peripheral surface which is divided into first and second areas in the longitudinal direction. A first conductive pattern is wound around the first area in the outer peripheral surface of the cylindrical member. The first conductive pattern has at least one antenna lead member wound around the first area in the outer peripheral surface of the cylindrical member in a helix fashion. A second conductive pattern is wound around the second area in the outer peripheral surface of the cylindrical member.
According to a thirtieth-first aspect of this invention, a composite antenna comprises a circuit board having a principal surface. A first hollow cylindrical member stands on the principal surface of the circuit board. The first hollow cylindrical member is made of insulator. The first hollow cylindrical member has a first center axis extending in a longitudinal direction perpendicular to the principal surface of the circuit board. The first hollow cylindrical member has a first outer peripheral surface. A second hollow cylindrical member stands on the principal surface of the circuit board with apart from the first hollow cylindrical member with a space. The second hollow cylindrical member is made of insulator. The second hollow cylindrical member has a second center axis extending in the longitudinal direction. The second hollow cylindrical member has a second outer peripheral surface. An antenna pattern film comprises a flexible insulating film and a conductive pattern printed on the flexible insulating film. The flexible insulating film comprises a first film portion, a second film portion, and a connection film portion for connecting between the first and the second film portions. The first film portion is wound around the first outer peripheral surface of the first hollow cylindrical member. The second film portion is wound around the second outer peripheral surface of the second hollow cylindrical member. The conductive pattern comprises first and second conductive pattern portions which are printed on the first and the second film portions, respectively. The first conductive pattern portion has at least one antenna lead member wound around the first outer peripheral surface of the first hollow cylindrical member in a helix fashion.
According to a thirtieth-second aspect of this invention, a composite antenna comprises a circuit board having a principal surface. A hollow cylindrical member stands on the principal surface of the circuit board. The hollow cylindrical member is made of insulator. The hollow cylindrical member haa a center axis extending in a longitudinal direction perpendicular to the principal surface of the circuit board. The hollow cylindrical member has an outer peripheral surface. An antenna pattern film comprises a flexible insulating film and a conductive pattern printed on the flexible insulating film. The flexible insulating film comprises a first film portion, a second film portion, and a connection film portion for connecting between the first and the second film portions. The first film portion is wound around the outer peripheral surface of the hollow cylindrical member. The conductive pattern comprises first and second conductive pattern portions which are printed on the first and the second film portions, respectively. The first conductive pattern portion has at least one antenna lead member wound around the first outer peripheral surface of the first hollow cylindrical member in a helix fashion.